The present invention concerns an apparatus for beam deflection, in particular for scanning microscopy, the light being deflectable by a first mirror arrangement that is alternatingly rotatable by a rotary drive. Apparatuses of the generic type are used in particular in scanning microscopy, in particular in confocal laser scanning microscopy. Merely by way of example, reference is made to DE 43 22 694 A1, in which a light beam is deflected with the aid of at least three mirrors, each having its own rotary drive.
DE 196 54 210 A1 discloses, per se, an optical arrangement for scanning a beam in two axes lying substantially perpendicular to one another, said arrangement having two rotationally driven mirrors, one of the two mirrors having a further mirror nonrotatably associated with it in a predefined angular position.
The mechanical rotary drives used for the mirrors or first mirror arrangements of the existing art are usually conventional galvanometers or resonant galvanometers. Galvanometers can be operated over a wide frequency range and are therefore versatile in terms of their utilization capabilities. With suitable activation, the zero point position of the galvanometer can be given an angular offset which corresponds to a constant deflection of the galvanometer axis. Because of their large moment of inertia, however, these galvanometers have an upper limit of a few hundred Hz in terms of their maximum attainable pivoting frequency or oscillation frequency. In addition, in some circumstances it is possible for undesirable oscillation-frequency-related deviations in the activation signal of a galvanometer (reference position) with respect to the actually established angular or rotational position of the mirror (actual position) to occur.
Resonant galvanometers, on the other hand, have a very high pivoting frequency or oscillation frequency, and the deviation between reference position and actual position is generally smaller than with conventional galvanometers. Resonant galvanometers can be operated only at the corresponding resonant frequency, however, so that versatile utilization is not possible. In addition, it is not possible with resonant galvanometers to establish an angular offset from the zero point position.